The central nervous thermoregulatory system, like other autonomic homeostatic systems, is greatly influenced by arousal states (wakefulness, nonREM and REM sleep). To understand the neural basis for these influences, we propose to investigate the processing of thermal information in the thermoafferent pathway and in the central integrative structure and how that processing is affected by arousal state changes. The central integrative structure in the thermoregulatory system is the preoptic anterior hypothalamus (POAH). The POAH is temperature sensitive and it receives thermal information from other sites including the skin and the spinal cord. The raphe nuclei, especially the nucleus raphe magnus (NRM), are important thermoafferent relays between ascending spinal tracts and the POAH. In experiments on Wistar rats and on rabbits we shall determine the influences of skin and spinal temperatures on the thermosensitivities of POAH neurons and the influences of arousal state changes on those relationships. The results from these experiments will enable us to evaluate hypotheses about how peripheral information is integrated by the POAH and how arousal state control mechanisms influence that integration; however, they will not enable us to distinguish between arousal state influences on thermoafferent versus central integrative structures. Therefore, we shall investigate the processing of thermoafferent information in the NRM as a function of arousal state. These experiments are made possible by our development of etched, Parylene coated microwire electrodes which enable long term extracellular recordings from POAH cells in unanesthetized, unrestrained animals.